Draw roll assembly for bag machine

ABSTRACT

The disclosure concerns a draw roll assembly for feeding a web to the seal bar of a thermoplastic bag making machine to regulate the nip pressure as required by the thickness of the web. To accommodate variations in the number of plies across the web, yet provide equal nip pressure between the draw rolls, one roll can be adjusted to operate in a non-parallel relation with the other roll. The draw roll assembly is disclosed in conjunction with a side weld bag making machine. A roll of plastic web is mounted on an unwind stand and traverses a folding board constraining the web to fold along its longitudinal median or along a line spaced from and parallel to the longitudinal median in the event it is desired to produce wicketed bags having a lip with a pair of holes in which is inserted a U-shape wire called a wicket. Downstream of the folding board a gusseter is provided to produce a fold which permits greater expansion at the bottom of the bag. The folded and gusseted web is driven by the draw roll assembly of the present invention and is fed thereby to a reciprocating transversely disposed seal and cutter bar which divides the web, at longitudinally spaced inter-vals, to produce individual bags. The bags are then transported to a table which is provided with devices for arranging the bags into a stack.

United States Patent Wech [4 1 June 5, 1973 t [5 DRAW ROLL ASSEMBLY FOR BAG ABSTRACT MACHINE The disclosure concerns a draw roll assembly for feed- [75] Inventor: Robert J. Wech, Green Bay, Wis. ing a web to the seal bar of a thermoplastic bag making machine to regulate the nip pressure as required [73] Asslgnee' FMC Corporation San Jose Cahf' by the thickness of the web. To accommodate varia- [22] Filed: Sept. 1, 1971 tions in the number of plies across the web, yet pro- [211 AppL NOJ 176,899 vide equal nip pressure between the draw rolls, one

Related US. Application Data Primary ExaminerRichard A. Schacher Assistant ExaminerGene A. Church A ttorney- Francis W. Anderson and C. E. Tripp Evers ..226/1 87 X roll can be adjusted to operate in a non-parallel relation with the other roll. The draw roll assembly is disclosed in conjunction with a side weld bag making machine.

A roll of plastic web is mounted on an unwind stand and traverses a folding board constraining the web to fold along its longitudinal median or along a line spaced from and parallel to the longitudinal median in the event it is desired to produce wicketed bags having a lip with a pair of holes in which is inserted a U-shape wire called a wicket. Downstream of the folding board a gusseter is provided to produce a fold which permits greater expansion at the bottom of-the bag. The folded and gusseted web is driven by the draw roll assembly of the present invention and is fed thereby to a reciprocating transversely disposed seal and cutter bar which divides the web, at longitudinally spaced intervals, to produce individual bags. The bags are then transported to a table which is provided with devices for arranging the bags into a stack.

3 Claims, 7 Drawing Figures P/HEPJTEDJUH 51975 SHEET 10F 6 H mHF-r INVENTQR. ROBERT J. WEOH ATTORNEYS PATENTEDJUH 5 197a SHEET 2 OF 6 INVENTOR. ROBERT J. NEON [WWW ATTORNEYS PATENTEU JUN 5 I975 SHEET 4 BF 6 INVENTOR. Roeem .1 ween BY WW ATTORNEYS PATENTEUJUZI 5 I975 SHEET 5 [IF 6 INVENTOR. "OBERT J. WEON ATTORNEYS DRAW ROLL ASSEMBLY FOR BAG MACHINE This application is a division of US. application Ser. No. 760,048, filed Sept. 16, 1968.

BACKGROUND OF THE INVENTION In order to attain a production rate of 200 or more quality thermoplastic bags per minute it is essential to design the bag making machine with features that provide: (a) positive control of the film during its unwinding from the parent roll; (b) maintenance of a fixed positional relationship between the parent roll supporting stand and the infeed frame of the bagging machine; when desired, a gusseting mechanism which provides a minimum drag to the film while insuring a gusset of constant depth; (d) web draw rolls whose nip pressure is evenly distributed and has the ability to apply a differential nip pressure from one end of the rolls to the other; (e) mechanism which will release the nip pressure in the event film movement is stopped to prevent the creation of flat spots on the film; (f) a seal bar which will maintain a uniform evenly distributed temperature throughout its length and one that is shielded to prevent heat loss to the film; (g) a seal bar drive arranged for a manual or automatic lift when desired or when web feeding is interrupted for any reason; (h) mechanisms to vary the length of the bag being produced while the machine is operating to correct or change the size of the bags accurately under operating conditions with no down time and (i) a bag transporting conveyor, which conventionally runs at higher speed than the film, including an easily adjustable positive control arrangement whereby adjustments can be made under operating conditions to insure that the trailing end of the bag is engaged by a conventional bag slow down mechanism to stack the bags so that their margins are in registration.

SUMMARY OF THE INVENTION In accordance with the present invention the film feeding draw rolls, which assist in feeding the film from the parent roll, are arranged so that the nip pressure applied to the film can be easily varied and if desired a differential nip pressure between the ends of the draw rolls can be produced. The preferred construction giving rise to this result comprises pneumatic cylinders or jacks arranged to apply a force to each end of the upper draw roll and the pressure to each cylinder can be equal, unequal or interrupted thereby removing all nip pressure. Removal of the nip pressure is usually desirable when the bag machine is stopped and this can be accomplished manually or automatically, as desired, thus preventing the creation of flat spots on the film.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 18, when viewed together along the break line R show the bag machine of the present invention in longitudinal section wherein the path of the web is shown by a broken line and the direction of web feed is indicated by arrows applied thereto,

FIGS. 2A and 28, considered together along the break line S, illustrates the bag machine in plan view,

FIG. 3 is an enlarged fragmentary portion, partially in section, showing the construction of the mechanism for changing the nip pressure of the draw rolls,

FIG. 4 is a fragmentary portion, on enlarged scale, taken along the line 3-3 of FIG. 28, showing the relationship of the seal bar, the seal roll and the draw rolls,

and

FIG. 5 is a section of FIG. 4, on a reduced scale, taken substantially along the line 5-5.

DESCRIPTION OF THE PREFERRED EMBODIMENT General Arrangement With reference to FIGS. 1A, 13, 2A and 28 it will be noted that the bag machine of the present invention is generally indicated by the numeral 20 and it comprises an unwind stand 22 (FIG. 2A) rotatably supporting core shafts 24 which in turn support film rolls 26. The web, designated by the letter W, unwound from the roll 26 is folded along a line parallel to its ends by a folding board or a V-board 28. When so called even edged bags are made the fold line is located at the longitudinal median of the web while the fold line for lipped bags is spaced from and parallel to the longitudinal median. FIG. 2A shows the V-board set up for producing lipped bags since the left hand margin of the web, identified by L. H., is laterally spaced from the right hand margin R. H. downstream from the V-board 28. The web then comes under the influence of a gusseting mechanism 30 which forms in inwardly directed fold on that portion of the web which defines the bottom of the completed bag. The fold is shown by a dotted line in FIG. 2A and is identified by numeral 32.

Referring to FIG. 1A it will be seen that the gusseting mechanism 30 is mounted on support arms 34 pivotally connected to a transverse rod 36 mounted to and extending between laterally spaced infeed frame members 38. Rotatably supported on the transverse rod 36 is a roller 40 which directs the web between a first set of infeed rolls of 42 connected to conventional nip pressure regulating means 43. The web is thence trained about a plurality of idler rollers 44, mounted on dancer arms 46, and rollers 48 extending between and rotatably mounted on the infeed frame members 38. The length of web accumulated in the path defined by the rollers 44 and 48 serves to provide a temporary supply which automatically increases or decreases in response to transient values of web tension. This arrangement tends to produce a constant value of web tension.

The bag machine frame comprises a base plate 50 having mounted thereon transversely spaced upwardly projecting side frame members 52 located substantially at the mid portion of the machine. At the discharge end, outfeed frame members 54 are also mounted on the base plate 50 and serve to support bag discharge control devices explained in detail hereinafter.

Referring again to FIG. 1A it will be observed that between the infeed frame members 38 and the midframe members 52 a horizontal accessory platform 56 is connected therebetween and it serves to support hole punching assemblies 58 mounted on a base plate 60. As

shown in FIG. 2B the base plate 60 is mounted on a rectangular frame 62 and is transversely adjustable on this frame. It is held in a selected transverse position by a lock screw 64. Longitudinal adjustment of the rectangular frame 62 carrying the hole punch assemblies 58 is accomplished by racks 66 and pinions 68. As shown diagrammatically in FIG. 2B the racks 66 are fixed to the inner surfaces of the side rails 56 while the pinions 68 are keyed to a transversely extending shaft 70 rotatably mounted in the rectangular frame 62. On one end of the shaft 70 a knob 71 is keyed for rotating the shaft 3 70 and consequently adjusting the longitudinal position of the hole punching assemblies 58.

from the sealing mechanism and transporting them to a stacking table 118 provided with adjustable stop Downstream of the hole punching assemblies 58 an 1 electronic web registration device 72' commonly referred to as a scanner, is likewise mounted for longitudinal and transverse adjustment. Longitudinal adjustment is accomplished by pinions 74 (FIG. 1A) in mesh 1 with the racks 66. The pinions 74 are mounted on a transverse shaft 76 rotatably carried in generally L shaped in frames 78. On the upright legs of the L frames 78 a transverse bar 79 is secured. Slidably mounted on the bar 79 is the scanner 72 which can be locked in any transverse position by a lock screw 80. On the horizontal leg of the L frame 78 atransverse bar 82 is mounted and it will be observed, by inspection of mechanism 104 and thus prevent wrinkling of the bag.

FIG. 1A, that its upper surface is in substantially the same plane as the web line. In order to insure repeated response of the scanner the upper surface of the transverse bar 82 is white in color so as to provide good contrast for detection of the printed registration mark. As is conventional the scanner is electrically connected to the control circuit of the bag machine to deenergize the Before the bags are discharged to the stacking table 118 they'come under the influence of conventional corrugating rollers 134 which serve to stiffen the bag in V the direction of movement so as to prevent distortion thereof as it is ejected to the stacking table 118. Before being discharged to the stacking table the trailing end of the bag is momentarily gripped by a slow down mechanism 136 of known construction.

clutch and simultaneously energize the brake thereby arresting the movement of the web for a sufficient 'p'eriod of time to allow the transverse seal bar to operate and thereby make the side weld for two longitudinally adjacent bags. After the seal bar completes its function the control circuitis then conditioned to releasethe brake and engage the clutch commencing web move ment.

As shown in FIG. 1B downstream of the scanner the web passes between intermittently operating drawrolls 84 associated with upper and lower sets of the stripper.

fingers 86 and 88, respectively, detachably mounted on transverse bars 90 and 91. The draw rolls are connected, as hereinafter will be more particularly described, with means, generally indicated by the numeral 92, for controlling the nip pressurethe draw rolls exert on the film and for removing the nip pressure when required, either selectively or automatically.

To resist the deflection of the draw rolls, particularly at their mid portion and thereby insure an even value of nip pressure along the length of the'draw rolls, a back-up roll 94, in rolling contact with the lower draw roll, is provided. The back-up roll 94 is rotatably mounted in a yoke 96 having a link extension 98 which forms one link of a parallel linkage mechanism 100. The vertical position of the back-up roll 94 and accordingly the backup force it will apply to the draw rolls 84 can be selected by adjusting a screw jack 102.

Immediately downstream of the draw rolls there is provided a vertically reciprocating sealing mechanism 104, cooperating with an intermittently rotating seal roll 106 for making the transverse seals in thefolded' web. These seals constitute the lateral margins of the bags. The seal mechanism is reciprocated by a pair of cams 108 (one of which is shown in FIG. 1B) keyed to" In order to synchronize the speed of the belt conveyor so that bags discharged therefrom are momentarily gripped at or adjacent their trailingedge, an elec- "trically; adjustable direct current drive arrangement 138 (FIG. 1B) is provided. The drive 138 includes a DC motor,,belt and pulley, not shown, for driving a v shaft 143. The shaft 143 has an adjustable pitch pulley 1447at its opposite end which drives a belt 145 trained about a pulley 146 mounted on ashaft 147. The shaft 147 provides powerfor the corrugating rollers 134. To

jdrivetheindex conveyor 112, a belt and pulley drive train, not shown, transmits power from the shaft 143 to the upper index conveyor drive roller which is adjacent the lowerset of corrugating rollers 134. For purposes of adjusting the pitch of the adjustable pulley 144, a tightener pulley 148 tensions the belt 145 and is carried by a stub shaft 150 mounted on an adjustable arm 152.

In accordance with the present invention the bag machine is provided with intermittently operating air loaded draw rolls for feeding the film to the seal bar. The upper draw roll is associated with fluid operated cylinders ofthe hydraulic or pneumatic type, but herein preferably of the pneumatic type, which regulate the nippressure between the rolls as required by the thickness of the film or whether gusseted or nongusseted bags are being produced. It is apparent that when producing gusseted bags one edge of the film assumes a reverse fold resulting in four plys of film. Thus maintaining the feed rolls parallel would result in either too much nip pressure at the gusset, if a required nip pressure were to be maintained at the mouth of the bag, or no nip pressure at the mouth of the bag, if the nip pressure at the'gusset were of a value required for positive film feeding. Accordingly, the upper feed roll of the present invention can be adjusted to assume a slightly non-parallel relation to the lower feed roll so that a substantially uniform nip pressure can be maintained along the width of the web when gusseted bags are beingproduced.

This feature of the present invention will be described in connection with the structure shown in V The ends of the draw roll 446 are mounted in bearings 448 (only one of which is shown in FIG. 5) secured in end blocks 450 pivotally connected to the side frames 52 by bolts 452 which are in effect pivot pins for the blocks 450. A lower draw roll 454 is mounted for rotation in the side frames 52 by bearings 456 and it has an extension 458 (on the right as viewed in FIG. 5) mounting a pulley 460 about which is trained a timing belt 462. A gear 464 fixed to the lower draw roll at a point adjacent the right side frame 52, as viewed in FIG. 5, meshes with an idler gear 465 which in turn meshes with a gear 466 keyed to the seal roll 106. This imparts rotation to the seal roll 106 in the same direction as the lower draw roll 454. Each of the draw rolls is provided with grooves 468 in which are disposed the upper and lower sets of stripper fingers 86 and 88 respectively. The upper stripper fingers 86 are individually bolted to the generally rectangular transversely extending support bar 90 having each end rigidly attached, by brackets 476, to the end blocks 450. On the other hand the lower stripper fingers 88 are mounted on the support bar 91 which is rigidly secured by similar brackets 478 to the side frames 52.

At a point intermediate the bearings 448, carried by the end block 450, and the pivot bolt 452, laterally outwardly extending pins 480 are threaded into the end block 450 to extend through generally a cruciform opening 482 formed in each of the side frames 52 (FIG. 5). Cylinders 484, preferably pneumatic and of the single acting type wherein only the head end is supplied with pressure fluid, are mounted on the upper surface of the side frame 52 and are located so that a plane containing the axis of the cylinders 484 also contain the axis of the pins 480. Each of the cylinders have a pro-' jecting rod 490 which makes contact with the upper surface of the pins 480 while the diametrically opposed lower surface of the pins 480 are in contact with springs 492 disposed within one leg 494 of the crusiform opening 482. According to this construction it should be readily apparent that since the upper feed roll 446 is rotatably mounted in the end blocks 450 which in turn are pivotally connected to the side frames 52 by the bolts 452, the interaction of the cylinders 484 and the springs 492 can control the pressure between the draw rolls 446 and 454. Also, when desired, differential loading can be applied to the ends of the upper feed roll 446. It is to be understood that suitable controls, conventional in the art, are provided for regulating and controlling the supply of pressure fluid to the cylinders 484.

Operation of draw rolls is as follows: When a new roll of film is being threaded through the bag machine the conduits 486 are not supplied with pressure fluid thus rendering springs 492 operative to rotate the end blocks 450 in a counterclockwise direction as viewed in FIG. 4. This, of course, raises the upper feed roll 446 and the stripper fingers 86 which are also carried by the end block 450. This provides sufficient space between the draw rolls 446 and 454 to facilitate threading the film therethrough. Upon commencing normal machine operation the control circuit energizes valves (not shown) which admit pressure fluid to the cylinders 484 by the conduits 486 extending the cylinder rods 490 which exert a downward force on the pins 480 overcoming in part the bias of the springs 492. Such action rotates the end blocks 450 about the pivot bolts 452 resulting in nip pressure between the feed rolls 446 and 454. The amount of nip pressure desired can obviously be regulated since the level of pressure of the actuating fluid supplied to the cylinders 484 can be easily regulated by the operator. As mentioned previously, in the event it is desired to equalize the nip pressure in such cases, for example, where gusseted bags are being produced, the value of pressure of the pressure fluid supplied to each of the cylinders 484 can be regulated to achieve this result and thereby constraining the upper feed roll 446 to assume a slight nonparallel relationship with the lower feed roll 454. v

Whenever the machine is stopped the control system can be readily energized to connect the conduits 486 to exhaust venting the cylinders 484 to atmosphere. Under this condition the springs 492 exert an upward force on the pins 480 rotating the end blocks 450 in a counterclockwise direction (as viewed in FIG. 4) about the pivot bolts 452. Accordingly it will be seen that the drawrolls utilized in the bag machine of the present invention can be controlled to apply a selected nip pressure and could be readily released whenever the machine is stopped. Further by being able to apply different values of pressure to the cylinders 484 the nip pressure can be substantially equalized when. producing gusseted bags.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention as set forth in the appended claims.

I claim:

1. In a thermoplastic bag making machine having means associated therewith for feeding and guiding an elongate web of thermoplastic film therethrough, said machine comprising means for feeding the thermoplastic film through said machine including opposed rotatable feed rolls mounted between side frames for receiving the thermoplastic film therebetween, and means mounting one of said rolls for lateral movement relative to the other; the improvement wherein said movable roll has both ends rotatably mounted in links pivotally supported on opposed side frames of the bag machine, a fluid actuated cylinder mounted on each side frame of said bag machine, said links including a portion engageable with said cylinders,-said cylinders being oper ative to pivot said links to effect pressure engagement of said rolls, and resilient means for pivoting said links to separate said rolls when fluid is exhausted from said cylinders.

2. The thermoplastic bag machine of claim 1 wherein said cylinders are independently pressure operable, the value of pressure of the motive fluid supplied to each of said cylinders being thus adjustable to apply a different value of nip pressure to each end of one of said feed rolls. I

3. Apparatus according to claim 1 wherein said links are pivoted to the confronting inner faces of the side frames of the machine, a laterally extending pin on each of said links disposed within an apertured portion of the associated side frame adjacent an edge of the side frame, each of said cylinders being mounted on the associated frame edge and having a piston rod extending through a frame aperture and in contact with one side of said pin, and a compression spring opposed to said piston rod and in contact with the other side of said pin for separating said feed rolls when said cylinders are de-energized. 

1. In a thermoplastic bag making machine having means associated therewith for feeding and guiding an elongate web of thermoplastic film therethrough, said machine comprising means for feeding the thermoplastic film through said machine including opposed rotatable feed rolls mounted between side frames for receiving the thermoplastic film therebetween, and means mounting one of said rolls for lateral movement relative to the other; the improvement wherein said movable roll has both ends rotatably mounted in links pivotally supported on opposed side frames of the bag machine, a fluid actuated cylinder mounted on each side frame of said bag machine, said links including a portion engageable with said cylinders, said cylinders being operative to pivot said links to effect pressure engagement of said rolls, and resilient means for pivoting said links to separate said rolls when fluid is exhausted from said cylinders.
 2. The thermoplastic bag machine of claim 1 wherein said cylinders are independently pressure operable, the value of pressure of the motive fluid supplied to each of said cylinders being thus adjustable to apply a different value of nip pressure to each end of one of said feed rolls.
 3. Apparatus according to claim 1 wherein said links are pivoted to the confronting inner faces of the side frames of the machine, a laterally extending pin on each of said links disposed within an apertured portion of the associated side frame adjacent an edge of the side frame, each of said cylinders being mounted on the associated frame edge and having a piston rod extending through a frame aperture and in contact with one side of said pin, and a compression spring opposed to said piston rod and in contact with the other side of said pin for separating said feed rolls when said cylinders are de-energized. 